MILWAUKEE — The defense behind Dallas Keuchel did its part with double plays to end the first, second and third innings.

But when you’re walking six, striking out one and allowing a deflating three-run homer, there isn’t much a defense can do.

Keuchel continued his fall from a great debut, allowing seven runs on seven hits and a career-high six walks Tuesday in the Astros’ 10-1 loss to the Milwaukee Brewers at Miller Park.

With the loss, the Astros closed the worst month in franchise history — a month that will be better remembered for their trading six major leaguers who represented 75 percent of the opening-day payroll — with a 3-24 record.

As veterans have been peeled away, it’s players like Keuchel who have received the opportunity and this second go-around with the major league club.

Including his four-inning start Tuesday, Keuchel has allowed 19 runs in 131⁄3 innings of starts against Arizona, Pittsburgh and Milwaukee. The problem is the walk/strikeout ratio, which continues to get worse. He’s now walked 25 batters (one intentionally) and struck out just 14 in his 39 innings.

After the game, the discussion was about an approach problem versus a command problem. Veteran catcher Chris Snyder wants to see the rookie attack more.

“You have to pitch with more aggression, pitch over the plate,” Snyder said. “He can mix speeds, he can cut it, he can sink it, and you’ve just got to trust it and throw it with conviction.”

Keuchel said his two walks of 2011 NL MVP Ryan Braun were the result of a careful approach, but he admitted to a mechanical problem that affected his command.

“Not so much trying to be careful, I mean to Braun a little bit, but it was just me getting out front and not finishing through,” Keuchel said.

Either way, the walks led to single runs in the first and second as double plays kept him out of major trouble. But in the third, he wasn’t so fortunate. He got his double play, but not before Carlos Gomez doubled, Braun walked and Aramis Ramirez homered.

At that point, it was 5-1, and the Brewers would pile on with Corey Hart’s three-run homer to welcome Chuckie Fick to the game. Chris Snyder’s homer was the only run the Astros would get against Yovani Gallardo, who went seven solid innings.